Method of centrifugal production of continuous metal filaments

ABSTRACT

A method for producing and concomitantly winding continuous metal filament in which a quenching wheel is used as a quenching element and in which sufficient pressure is exerted on the filament just beyond the point of solidification to counteract the tensional stress exhibited by the winder on the filament.

United States Patent Kavesh Dec. 24, 1974 [5 METHOD OF CENTRIFUGALPRODUCTION 989,075 4/1911 Staples 164/276 01: CONTINUOUS METAL FILAMENTS2,172,018 9/1939 Spencer 164/87 D UX 3,677,481 7/1972 Haley et al 164/82X Inventor: Sheldon Kai/98h, PP y 3,812,901 5/1974 Stewart et al 164/87[73] Assignee: Allied Chemical Corporation, New FOREIGN PATENTS ORAPPLICATIONS York 1,040,766 9/1966 Great Britain .1 [64/82 [22] Filed:Apr. 6, 1973 Primary Examiner-R. Spencer Annear [21] PP 348,814Attorney, Agent, or FirmArthur J. Plantamura 52 us. 01 164/87, 164/276,264/164 1 1 ABSTRACT [51] Int. Cl B22d 11/06 A method for producing andconcomitantly winding [58] Field of Search 164/87, 276, 278; 264/ 164,continuous metal filament in which a quenching wheel 264/165 is used asa quenching element and in which sufficient pressure is exerted on thefilament just beyond the [56] References Cited point of solidificationto counteract the tensional UNITED STATES PATENTS stress exhibited bythe winder on the filament. 745,786 12/1903 Cole 164/276 4 Claims, 3Drawing Figures K; '4 NIPP1NG PRESSURE 10 o PATENTED 1153241974 3,856.074 sum 1 i 2 PRESSURE NIPPING METHOD OF CENTRIFUGAL PRODUCTION OFCONTINUOUS METAL BACKGROUND OF THE INVENTION The present inventionrelates to an improvement in the production of continuous metalfilaments of indefinite length which are normally wound on spools. Morespecifically, for the purposes of the invention, filament is herein usedto represent a slender body whose trans-.

verse dimensions are much less than its length. In the present context,the filaments may be ribbons, sheets, wires or irregular cross-sections.

During recent years, researchers developed various methods'directed tothe formation of metal filaments which avoid the inherent difficulties'of previous casting and rolling techniques. These methods include, forexample, melt extraction and chill block spinning.

Melt extraction connotes a process wherein a cold quenching wheelrotates at high velocity in kissing, i.e., skimming, contact with aliquid metal surface. The molten metal wetting the wheel is'carried upout of the molten bath, where it solidifies and thereby shrinks awayfrom the wheel and is flung off by centrifugal action. The meltextraction techniques discussed herein are to be distinguished fromother extraction methods such as those described in U.S. Pat. No.1,025,848 to Wagner and U.S. Pat. No. 2,074,8l2 to Sendzimer, whichprimarily employ a casting technique in which the cold wheel issubstantially immersed in the liquid metal and in which the rotationalvelocity of the wheel is appreciably lower than in the melt extraction.

Chill block spinning is exemplified by U.S. Pat. No. 905,758 to Strangeand Pirn, U.S. Pat. No. 2,825,108 to Pond, U.S. Pat. No. 2,886,866 toWade,and U.S. Pat. No. 2,899,728 to Gibbons. In this process, a free jetof molten material is impinged upon a moving chilled quenching surface,preferably a rotating wheel. The molten jet is solidified in the form ofa ribbon or sheet and is flung away from the rotating chill surface bycentrifugal action.

one important disadvantage in the melt extraction and chill blockspinning processes as presently employed is that they produce long, butnot genuinely continuous filaments. The flinging action which removesthe filament from the wheel induces an oscillating or whipping motion inthe filament which inevitably causes breakage. Presently filaments areproduced with a maximum length of only about 300 meters. Continuousmetal filaments in the range of" 1,000 to greater than 30,000 meters inlength are required for such applications as strapping, springs,filament-wound vessels, aerospace skins and the like. n

An additional problem encountered. in the melt extraction and chillblock spinning processes is that of winding the lengths of filamentformed. The incorporation of a tension regulated winder or similarcollecting device intothe system results in, a great amount of stressbeing transmitted back to the solidification zone, a factor which,contributes to the breakage of the filaments. Since the down time causedby rethreading the filaments onto the winder after breakage isconsiderable, the metal filaments must be wound in a separate operation.There is obviously a need for a method to produce continuous lengths ofmetal filaments which can be wound concomitantly with production.

SUMMARY OF THE INVENTION It is therefore an object of this invention toproduce continuous metal filament, or ribbon or sheet.

It is another object to produce a continuous filament or sheet which canbe automatically collected in a neat coiled package concomitantly withits production.

These and other objects and advantages will become apparent from thedescription and examples provided herein.

Accordingly, this invention is directed to an improvement in theproduction of metal filaments, ribbons or sheets. In the production ofthese materials using a rotating wheel as the quenching source, theimprovement comprises establishing a tension-free zone by positioning apressure exerting means in nipping contact with the quenching sourcebeyond the point of solidification; ideally, just at the point whereshrinkage of the filament causes detachment from the quenching source.In an additional aspect of the invention, the filament can then bedirected from the nipping means and wound on a tension controlled winderor other collecting means such as a spinning bucket. Thus, the nippingaction isolates the fragile filament or sheet in the solidification zonefrom the tension exerted by the winder. The continuoustension exerted bythe winder and/or tension regulating mechanism used in conjunction withthe winder prevents whipping, thereby avoiding filament breakage andenabling production of a truly continuous filament.

The nipping means employed may be any device having freedom of movementand capable of exerting sufficient pressure on the solidifying filamentto counteract the stress transmitted by the winder and also by inherentcentrifugal and gravitational forces thereby preventing breakage. Thedevice may be in the form of a bar, a blunt blade or preferably, a coldwheel freely rotating or driven at the same surface velocity as thequench wheel. In this regard, it is to be noted that the role of thenipping device is not merely that of a guide. It is intrinsic to thisinvention that pressure be exerted by the device onto the solidifyingfilament and not merely that the filament be guided around the device.The mere positioning of a guide wheel at the point of solidificationdoes not prevent breakage of the filament since it does not counteractthe centrifugal or gravitational forces or the tensional stresstransmitted by the winder. The arrangement of the invention requires, asan essential facet, freedom of movement so that the nipping device canreadily adapt to use in forming filaments of various thickness and doesnot ficients of friction between the filament and the quench roller andthe filament and the nip roller respectively.

This novel method for producing continuous wound filaments could beeasily adapted to any process for preparing filaments in which thequenching step is carried out on a chill wheel, drum, etc. and thefilament is separated after solidification by centrifugal force.

This method is particularlyuseful in very high speed forming operationswhere formation and subsequent winding occurs very rapidly and a greatamount of stress is transmitted to the solidifying filament.

While this application is directed to the use of the nipping pressuremeans in conjunction with the use of a tension regulating winder, itisobvious that the invention also includesthe production of long orcontinuous filaments which are not wound concomitantly with theirproduction but are collected in another manner.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 illustrates diagrammatically anapparatus which uses a wheel melt extraction in conjunction withDESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2'arerepresentative of the novel aspects of the present invention. In FIG. 1,a cold wheel rotates in kissing contact as shown at 12 with surface -17of a liquid metal 18 confined in a suitable reservoir 11. The moltenmetal solidifies on the surface 19 of the wheel 10 and is carried up outof the reservoir 11, and at a point 13 at which it begins to shrink awayfrom the wheel 10 it comes into contact with a second cold wheel 14which exerts a nipping pressure (between wheels 10 and 14) on thefilament 15. The filament 15 is then continuously drawn by aconventional tension control device 16 and wound onto' a roller 17. Theposition of the nipping roller 14 and the pressure which it exerts onthe filament 15 are controlled by means of a pressure exerting mechanismsuch as an air cylinder operating-through a conventional connecting linkbetweenthe roller 14 and the cylinder (not shown).

During start-up of the process, the nipping roller 14, as shown in FIG.1a is swivelled to a remote position. Rotation of the quenching wheel 10is initiated and the level of liquid metal 18 in the reservoir 11 israised by opening a valve from a supplemental reservoir (not shown).When the liquid metal 18 contacts the quench wheel 10, at the contactpoint 12, formation of the metal filament commences. The filament isflung away by centrifugal action at the point 13 and the nipping roller14 is then converged toward quenching wheel 10 so that the filament 15is held between these rotating elements and the filament is conveyed viaa tension control regulator 16 to a winder.

The pressure exerted by the nipping roller 14 on the filament 15isolates the fragile solidification zone 12 to 13 from the tension ofthe winding arrangement and prevents filament breakage from this sourceand/or from whipping of the filament as it is drawn by the winder. Themetal filament 15 is then continuously wound up in packages whoselengths are determined only by the capacity of the winder. Molten metalis admitted to the reservoir '11 to maintain the continuous filamentforming process.

Moderate changes in the rotational speed of the quench roller 10 orchanges in the thickness of the filament do not substantially affect thewinding process or continuity of the filament. As noted hereinabove, anair cylinder or other suitable positioning and/or pressure applyingdevice may be used to. hold the nip roller against the quench rollerthereby permitting the filament thickness to vary without reduction ofnipping pressure. I

In FIG. 2, an alternate apparatus is employed to provide a similarresult. In FIG. 2, the melt 28 is contained in an insulated container 29provided with heating element 31. During start-up of the process, thenipping roller 24 is swiveled to a remote position in a manner asdescribed in connection with FIG. la. Rotation of the quenching wheel 21is initiated and inert gas 34v is admitted to the melting container orvessel 29. A molten jet 32 is extruded from a suitable opening 33 in thebottom of the container 29 and impinges upon the rotating quench wheel21 to form a filament 30. The filament has a tendency to be flung awayby centrifugal action at that point 23. The nipping roller 24 isconverged on wheel 21 and the solidified filament 25 is conveyed to atension controlled windbar 26 to a storage roller 27 as previouslydescribed in connection with FIG. 1.

The nipping rollers 14 and 24 are preferably freely rotating,lightweight devices supported byroller bearings. They may comprise asolid cylinder, a hollow cylinder, or a composite cylinder. A desirableconfiguration has been foundto be a composite hollow cylinder having anouter shell consisting of a material of a high coefficient of frictionbonded to an inner annular tube the present invention are any materialswhich are wear resistant under the temperatures of use. Illustrativeexamples include organic impregnated woven asbestosbrass wirecompositions manufactured by Raybestos- Manhattan Corporation anddesignated as U898 and US2010. The inner core may be steel or similarhigh strength material.

The wind-up mechanism may be used alone or in conjunction with aseparate tension regulating device as 16 and 26. If the wind-upmechanism is used alone, it should contain a means of regulating tensionas for example by means of a slip clutch on the winding drum.Alternatively, separate tension regulating devices may be employed;illustrative devices could be counterbalanced, spring-loaded or balancedby means of an air cylinder.

The invention will be further described in the following illustrativeexamples:

EXAMPLE 1 A grey iron alloy containing 3.4 weight percent carbon, 2.2weight percent silicon, 0.6 weight percent manganese, 0.2 weight'percentphosphorus and 0.01 percent sulfur was melted at l,200 C.- in aconventional apparatus for melt extraction similar to that depict'edschematically in FIG. 1. However, a nip roller similar to roller 14 wasnot utilized.

The quenching wheel was constructed of oxygen free high conductivitycopper of 8 inch outside diameter and provided with internal channelsfor thecirculation of cooling water. Cooling water was admitted througha rotary union on one. side of the hollow quenching wheel shaft and waswithdrawn through a rotary union on the opposite side. The face width ofthe quenching wheel was one inch.

Rotation of the quenching wheel was commenced at 1,800 revolutions perminute. The level of the grey iron melt in the crucible was raised byopening a valve to the connecting reservoir. The liquid metal surfacewas brought into kissing contact with the rotating quench wheel. Asolidified filament of .1 inch width and 0.000l-0.008 inch thickness wasformed on the face of the quench wheel and was flung away by centrifugalaction. The arcuate. path of the solidified filament commenced at atangent to the surface of the quenching roll, traveled upward at anangle of 30 60 to the horizontal, reached a point of maximum elevationand finally turned downward and fell into a catch basin on the floor.The path of the filament was severely affected by whipping oscillationsinduced by random changes in the point and angle of departure of thefilament from the quench roll. The filament remained continuous forperiods of several seconds until at irregular intervals the oscillationscaused the filament to break off near the quench roll.

The filament was seized near the point of departure from the quench rolland guided to engage the winder. At filament tensions of ll gramsfilament oscilla- 6 ribbon 1 inchwide by 0.008 inch thickness wereproduced for eight hours without experiencing a break.

The coefficients of dynamic friction for several metal systems are givenby The Handbook of Chemistry and Physics, 51st Edition, pp. Fl5-F 17.The coefficient of friction between grey iron and steel is 0.4. Thecoefficient of friction between steel and a copper film (8 kg. load) isgiven as 0.2. Taking the latter to be the same as the frictioncoefficient between grey iron and copper, the necessary minimum nip rollpressure was obtained from equation (1) by making the followingsubstitutions.

tions persisted causing eventual breakage. During the periods betweenbreaks, only a relatively unsatisfactorily loosely wound filament wasproduced. With higher winding tensions the filament ruptured in thesolidification zone immediately as it was connected to the winder.

EXAMPLE 2 The apparatus of Example 1 was modified by utilizing a nippingroller 14 as depicted in FIG. 1. The nipping roller was of 4 inchoverall diameter and consisted of a 4 inch diameter hollow steelcylinder of one-quarter inch wall thickness. In addition, the nip rollerwas of 2 inch face width and was supported by a one-half inch steelshaft mounted on roller bearings. It was freely rotatable.

7 The melt'extraction process wasstarted with grey iron alloy asdescribedin Example 1. The nip roller 14 was swiveled to the remoteposition depicted in FIG. la, the path of the centrifugally flungfilament passed above and between the quench roll and the nip roll. Thenip roller was then actuated to the closed or converged position bymeans of an air cylinder which pressed the filament against thequenching wheel with a force of 30 pounds. This pressure was chosen byreference to equation (1) as will be explained below. The filament wasseized as it passed through the nip zone and guided to engage thewinder. The filament was then continuously wound without interruption at10 pounds tension. Tight, uniform packages of grey iron T= l0 lbs/in Munfrom equation (I) P a 16.67 lbs/in To provide a margin of safety, thenip roll pressure was set at 30 pounds.

EXAMPLE 3 An alloy formulated to be amorphous upon quenching was chargedin an apparatus for chill block spinning similar to that depictedschematically in FIG. 2. However, no nip roller was provided. Thequenching wheel iron, 39- atomic percent nickel, l4 atomic percentphosphorus, 6 atomic percent boron and 3 atomic percent aluminum. It wasmelted in an argon atmosphere at l,000 C. The quench wheel was set intomotion at 1,800 rpm and the molten alloy extruded through an orifice of0.010 inch diameter at 300 cm/sec'. The molten jet traversed a 1 inchair gap and impinged upon the surface of the rotating quench wheel. Asolidified filament 0.025 inch wide by 0.002 inch thick was formed andwas flung away by centrifugal action. The path of the solidifiedfilament commenced at a tangent to the surface of the quench wheel,traveled downward at an angle of 3060 to the horizontal and terminatedon the laboratory floor.

The filament was seized near the point of departure from the quench rolland guided to engage the winder. Attempts were made without substantialsuccess to wind the filament continuously under controlled tension. Atfilament tensions of l-l 0 grams filament oscillations persisted causingeventual breakage. During the periods between breaks, only anunsatisfactorily loose filament winding was produced. With higherwinding tensions the filament was torn apart in the solidification zoneimmediately as it was connected to the winder.

EXAMPLE 4 The apparatus of Example 3 was modified by provision of anipping roller depicted as 24 in FIG. 2. The nipping roller 24 was of 4inch overall diameter and consisted of a 4 inch diameter hollow steelcylinder of -24. The nip roller was then actuated to the closed orconverged position as shown in FIG. 2. by means of an air cylinder (notshown) which pressed the filament against the quenching wheel with aforce of pounds. This pressure was chosen by reference to equation (1)as explained below. The filament was seized as it passed through the nipzone and guided to engage the winder. The filament was then continuouslywound without interruption at l-pound tension. Tight uniform packages ofmetal ribbon 0.025 inch wide by 0.002 inch thickness were produced for 8hours without experiencing a break.

The coefficients of dynamic friction for several metal systems are givenby The Handbook of Chemistry and Physics, 51st Edition, pp Fl5-Fl7. Thecoefficient of friction between cast iron and steel is 0.4. Thecoefficient of friction between steel and a copper film (8 kg load) isgiven as 0.2. Taking these to be the same as the friction coefficientbetween the alloy spun here and the necessary steel and copper, minimumnip roll pressure was obtained from equation (1) by making the followingsubstitutions.

T= 1.0 lbs/in. F'QR MIR 04 from equation P z 1.0/0.2 +0.4 P 2 1.67lbs/in.

To provide a. margin of safety, the nip roll pressure was set at 5pounds. I

I claim:

1. In a method for the production of metal filaments from a moltensource using a rotating quenching wheel as a quenching element, theimprovement which comprises exerting sufficient nipping pressure on, theformed filament at a point on-the quenching wheel beyond the point ofsolificiation of the filament and prior to the point said filament isseparated from the quenching wheel by centrifugal action to retain thefilament against the quenching wheel and subsequently collecting thefilament.

2. The method of claim 1 wherein the formed filament is directed onto atension regulated winding device and the nipping pressure exerted issufficient to counteract the tensional stress exhibited on the filamentby the winder and to create a tension free zone in which continuouslengths of filament can be produced and concomitantly wound.

3. The method of claim 2 wherein the nipping pressure in lbs/inchexerted is at least as great as that derived from the equation:

where T is the winding tension in lbs/inch of filament width and ,u andm are coefficients of friction between the filament and quenching wheeland the filament and nip roller respectively.

4. The method of claim I- wherein the nipping pressure is exerted by acold nipping wheel.

' g y UNITED STATES PATENT OFFICE 5 9 CERTIFICATE OF CORRECTION patent3,856,074 Dated December 24. 1974 Inventor) Sheldon Kavesh It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 4, line 41, "or" should be of Column 2, line 60, the equationshould read:

P T/(UQR UNR) Column 6, line 17, the equation should read:

- P i l0/(0.2 O. 4)

. Column 8, line 1, the equation should read:

Claim 3, column 8, line 26, the equation should read:

En'gncd and Scaled this seventeenth Day Of February 1976 [SEAL] Attest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner oflaremsand Trademarks

1. In a method for the production of metal filaments from a moltensource using a rotating quenching wheel as a quenching element, theimprovement which comprises exerting sufficient nipping pressure on theformed filament at a point on the quenching wheel beyond the point ofsolificiation of the filament and prior to the point said filament isseparated from the quenching wheel by centrifugal action to retain thefilament against the quenching wheel and subsequently collecting thefilament.
 2. The method of claim 1 wherein the formed filament isdirected onto a tension regulated winding device and the nippingpressure exerted is sufficient to counteract the tensional stressexhibited on the filament by the winder and to create a tension freezone in which continuous lengths of filament can be produced andconcomitantly wound.
 3. The method of claim 2 wherein the nippingpressure in lbs/inch exerted is at Least as great as that derived fromthe equation: T/ Mu QR + Mu NR where T is the winding tension inlbs/inch of filament width and Mu QR and Mu NR are coefficients offriction between the filament and quenching wheel and the filament andnip roller respectively.
 4. The method of claim 1 wherein the nippingpressure is exerted by a cold nipping wheel.